Dental treatment or examination apparatus

1. Field of the Invention

The invention relates to a dental treatment or examination apparatus with a dental treatment or examination instrument. Additionally, the invention relates to a method for controlling a dental treatment or examination instrument and a method for monitoring a dental treatment or examination instrument.

2. Description of the Related Art

A tooth is essentially composed of three components, specifically the dentin; the enamel that coats the dentin for the latter\'s protection; and the pulp, also called dental pulp or, colloquially, the dental nerve that comprises the nerve fibers and blood vessels of the tooth. The pulp can be subdivided into the coronal pulp, which is found in the crown, and the radicular pulp, found in the root. The pulp tissue is particularly sensitive to thermal stimuli. Temperatures above 42° C. can thermally damage the pulp tissue, and this can lead to the pulp tissue dying off.

Information relating to the size and extent of the coronal pulp is of interest when preparing teeth so as to avoid inadvertent opening of the coronal pulp during the preparation of a tooth. Radiological display methods often are used to determine the extent of the pulp. However, the actual dimensions of the pulp often are reproduced incorrectly in radiological displays such as bitewing radiographs. It is possible for the extent of the pulp to be underestimated, particularly in the region of the molars.

DE 10 2005 044 889 A1 discloses a dental examination and/or treatment tool that comprises a lumen in which an imaging catheter is arranged for recording image data of an examination and/or treatment region. The imaging catheter is used for recording image data after a partial pulp removal in the root canal. In particular, the imaging catheter can be an OCT catheter for carrying out optical coherence tomography.

Dental diagnosis equipment with an optical camera and OCT equipment is known from the Patent Abstracts of Japan 2004344260A. The optical camera records a surface image of a tooth region in which a scan then is recorded by the OCT equipment.

It is not the object of either DE 10 2005 044 889 A1 or the Patent Abstracts of Japan to avoid inadvertent opening of the pulp. In particular in DE 10 2005 044 889 A1, the opening of the pulp is intended.

Therefore, there is the need for dental treatment and examination apparatuses that help avoid inadvertent opening of the pulp. Furthermore, there is the need for methods to control and monitor such equipment, which methods contribute to avoiding the inadvertent opening of the dental pulp.

It is therefore an object of the invention to provide a dental treatment or examination apparatus that helps avoid inadvertent opening of the dental pulp. It is another object of the invention to provide a method for controlling a dental treatment or examination instrument, which method contributes to avoiding the inadvertent opening of the dental pulp. It is a third object of the invention to provide a method for monitoring a dental treatment or examination instrument, which method contributes to avoiding inadvertent opening of the dental pulp.

A dental treatment or examination apparatus according to the invention comprises a dental treatment or examination instrument, a white light interferometer, a control unit, an analysis device and a warning and/or stopping device that is designed to emit a warning signal and/or stop the dental treatment or examination instrument. The white light interferometer comprises a measurement beam branch, a reference beam branch, an emitter for emitting measurement radiation in the direction of a tooth to be treated or examined, a receiver for receiving measurement radiation reflected by the tooth to be treated or examined, superposition equipment for superposing reference radiation and reflected measurement radiation, and a detector for detecting the superposed radiation and for generating an interferometric signal representing the superposed radiation. The dental treatment or examination instrument has a distal end in which the emitter and the receiver are arranged and is designed to be brought close to the tooth of a patient to be treated or examined. In particular, the emitter and the receiver of the dental treatment or examination instrument can be identical. The control unit is assigned to the white light interferometer and comprises a control program that causes the white light interferometer to carry out depth scans of the treatment or examination object. The control program can cause such depth scans to be carried out continually, or only in the presence of an actuating signal. The depth scans sometimes also are referred to as A-scans. The analysis device is connected to the detector of the white light interferometer for receiving the interferometric signal. It is designed to determine the distance of the pulp of the tooth to be treated or examined from its current surface and output a distance signal representing the distance. The current surface of the tooth can either be the actual surface of the tooth or the surface of a tooth opening, such as a bore. The warning and/or stopping device is connected to the analysis device for receiving the distance signal and is designed to emit a warning signal and/or stop the dental treatment or examination instrument when the distance reaches or falls below a predetermined minimum distance. In particular, the dental treatment or examination apparatus according to the invention can also be designed as an examination apparatus that only comprises a white light interferometric probe as a dental examination instrument.

The apparatus of the invention makes it possible to examine a depth region in the tooth using white light interferometry, without the tooth having to be opened for this purpose. In particular, the depth scan makes it possible to easily determine the boundary between the dentin and the softer pulp, and the distance of this boundary from the current surface. For this purpose, a depth scan with a depth range of 1 to 3 mm generally suffices. Hence, the depth of the pulp below the surface of the tooth or the area of a tooth opening can be determined by an external examination. A warning signal is emitted if it is determined in the process that a predetermined minimum distance between the surface and the pulp is reached. The warning signal alerts the dental treatment staff to the fact that the predetermined minimum distance between the surface and the pulp has been reached. It is also possible to stop the treatment apparatus when the minimum distance is reached if the emitter and detector of the white light interferometer are integrated in a dental treatment apparatus, for example a dental drill. In the case of the drill, this would mean that the drill is switched off as soon as the distance reaches or falls below the minimum distance. Inadvertent opening of the pulp can be avoided to a large extent by means of the warning signal or by switching off the treatment instrument. It is also possible for the treatment staff to carry out the treatment with increased care when approaching the pulp after the warning signal has been emitted so that the inadvertent opening of the pulp is avoided in the case where the distance must fall below the minimum distance for medical reasons.

The measurement beam branch of the dental treatment or examination apparatus according to the invention may comprise an optical fiber with a distal fiber end arranged in the distal end of the dental treatment or examination instrument. The emitter and receiver can be formed by the distal fiber end. This affords the possibility of implementing the measurement beam branch with very small dimensions in the region of the dental treatment or examination device so that the emitter and the detector can be guided very close to the surface of the tooth, and in particular very close to the surface of even a small bore in the tooth. Furthermore, small fiber diameters afford the possibility of illuminating a surface region with a very small lateral extent. Thus, a very high lateral resolution can be obtained by the depth scan, which is particularly advantageous if a lateral scan also is intended to be carried out to determine the lateral course of the boundary between pulp and dentin.

The dental treatment instrument can be a drill with a drill tool having a distal drill tool end, with the distal fiber end being arranged in the distal drill tool end or in its vicinity. There is the risk of inadvertently opening the pulp when preparing a tooth by means of a drill. Hence, the apparatus of the invention can be used with particular advantage in a dental treatment instrument that has a drill to avoid inadvertently opening the pulp. In this case, the optical fiber can be arranged in the rotational axis of the drill tool of the drill so that the center of the current surface of the bore is always measured by the depth scan in a simple fashion. Alternatively, the optical fiber can be arranged outside of the drill tool such that the distal fiber end illuminates that location at which the distal drill tool end is located. In that case it is not necessary to arrange the fiber end in a rotating drill tool.

The control unit of the dental treatment or examination apparatus according to the invention can be provided with a control program that causes the white light interferometer to carry out depth scans of the treatment or examination object continually. This ensures that the distance of the surface to the pulp is monitored continually. The warning signal or stop signal then can be emitted as soon as the minimum distance is reached. Alternatively, it is possible that the dental treatment or examination apparatus comprises an actuating element to be operated by the treatment or examination staff. The actuating element is connected to the control unit that emits an actuating signal for actuating a depth scan. By way of example, the actuating element can be a button on the handpiece, a foot switch, et cetera. In this refinement, a depth scan is carried out only when required. This refinement is expedient in particular when the dental treatment and examination apparatus only comprises a white light interferometric probe as the sole examination instrument.

A lateral course of the boundary between the pulp and the dentin can be determined by providing the measurement beam branch of the white light interferometer with a scan apparatus that laterally offsets the surface area irradiated by the measurement radiation on the tooth to be treated or examined. Hence, it is possible to undertake a lateral scan (a so-called B-scan), which leads to one depth scan being carried out in each case at a number of points of a lateral region. This makes it possible to determine the course of the pulp over a relatively large surface area. In particular, this also makes it possible to emit the warning signal or the stop signal when the distance in a region that does not correspond to the current treatment region, but lies in its direct vicinity, has fallen below the minimum distance.

In a first method according to the invention for controlling a dental treatment instrument, a depth scan of the treated or examined tooth region is undertaken during the dental treatment by means of a white light interferometry method. The distance of the surface of the treated tooth region from the pulp of the tooth then is determined from the depth scan. The dental treatment instrument is stopped if the distance reaches or falls below a predetermined minimum distance. In this fashion it is possible to avoid unintended opening of the pulp by stopping the treatment instrument in good time by means of a white light interferometric measurement of the distance of the pulp from the surface.

In a second method according to the invention, a dental treatment or examination instrument is monitored by means of a depth scan of the treated or examined tooth region being undertaken during the dental treatment or dental examination by means of a white light interferometry method. The distance of the surface of the treated or examined tooth region from the pulp of the tooth then is determined from the depth scan. A warning signal is emitted if the distance reaches or falls below a predetermined minimum distance. In the process, the warning signal can prompt the examination staff to end the treatment or examination or, should this not yet be possible, to continue with increased care.

A lateral scan of the treated or examined tooth region can be carried out in both methods in addition to the depth scan so as to also be able to determine the distance of the pulp from the surface in regions that are adjacent to the current treatment or examination region. A depth scan then can be undertaken at every lateral point.

A depth scan can be carried out continually or only after the treatment or examination staff actuate an actuating apparatus (such as a button on the handpiece, a foot switch, et cetera), independently of whether a lateral scan is carried out or not. Continually carrying out depth scans lends itself to those cases where action has to be taken as soon as the minimum distance is reached. If reaching the minimum distance does not mark a critical boundary, but only serves to inform the treatment or examination staff, it can suffice to carry out a depth scan only on occasions initiated by the staff.

In both methods according to the invention, the depth scans can be carried out to a depth of 1 to 3 mm, starting from the surface. This depth is generally sufficient to avoid the inadvertent opening of the pulp.